I've watched them all so far and recall that wolf pack video on the internet months ago. My favorites so far are either the killer whales hunting in packs causing waves to wash over their victim or the time lapse of the water freezing the starfish.

I haven't watched the behind the scenes episode yet. I saw the disclaimer that some scenes are shot under controlled conditions for the protection of the animals. They did such an amazing job with it that you can't tell those from the ones shot in the wild. The whole show is fascinating.